Distributions of divalent transition metal ions between coexisting ferromagnesian silicates

6 Distributions of divalent transition metal ions between coexisting ferromagnesian silicates 

The interpretation of relative enrichments of iron in coexisting silicates presented in 7.5 hinges on the availability of CFSE data for Fe2+ ions in coordination sites for a wide variety of rock-forming minerals. The CFSE data are more sporadic for other transition metal ions in coexisting minerals, particularly the divalent cations. 

The CFSE values of Ni2+-bearing minerals summarized earlier in table 5.19 decrease in the order 

nickel should be enriched relative to pyroxenes in dense Upper Mande minerals (e.g., silicate spinel and olivine) and their low-temperature alteration products (e.g., gamierite). 

In the absence of complete CFSE data for divalent cations in all ferromagne-sian silicates, qualitative arguments may be used to deduce relative enrichments of these ions in coexisting minerals using crystal chemical information summarized in chapter 6 ( 6.7 and 6.8). 

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